Scientists say they have for the first time examined the blood of a mother for genetic signs of disease in the fetus. The technique could one day offer an alternative to invasive methods of prenatal diagnosis such as amniocentesis and chorionic villus sampling (CVS), which slightly increases the risk of miscarriage.
Yuet Wai Kan and colleagues at the University of California, San Francisco, extract fetal cells from maternal blood to see if the fetus had the genes for two recessive diseases: sickle cell anemia and a similar condition called beta thalassemia. Their findings are published in the November Nature Genetics .
The method relies on the fact that a handful of fetal blood cells leak into the blood of the mother through the placenta. Scientists have isolated the fetal red blood cells in the blood of two pregnant women, each carrying one of these diseases. They stained cells with an antibody directed against a fetal protein and plucked with a small needle. Standard DNA analysis revealed that neither had inherited both copies of the gene necessary to develop symptoms, and CVS tests confirmed the results. One drawback, Kan said, is that the test does not work on fraternal twins as he can not discern what fetal cells come.
A noninvasive test performed in early pregnancy would be "very attractive" for many women, says Mary Mahowald, a bioethicist at the University of Chicago. But first, this procedure should be more people vetted. "We have shown that this is possible," said Kan, "but we need other tests to show how accurate it is."
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